1. Field of the Invention
The present invention relates to opening/closing mechanisms for a keyboard cover of a keyboard instrument such as an electronic piano.
2. Description of the Related Art
As disclosed in Unexamined Published Japanese Patent Application 10-198339, in order to render compact a case for a keyboard instrument the keyboard cover is composed of front and back cover halves hinged foldably. Thus, when the cover is opened so as to expose the keyboard, the front and rear cover halves are accommodated folded within the case. When the cover is drawn out from the case, the front and rear cover halves are extended substantially flat so as to cover the keyboard.
More particularly, when the front cover half is moved backward to be accommodated within the case, the rear cover half is also moved backward from the keyboard while being gradually bent at the hinge. When the front cover half is accommodated within the case, the rear cover half is accommodated upstanding with its rear end down. When the rear cover half is bent, the front cover half is rendered unstable at its rear part, and in order to avoid this situation, supported at its rear end by an auxiliary mechanism.
More particularly, the auxiliary mechanism comprises a forward and backward turnable normally upstanding support plate that supports the front cover half at its rear end within the case. When the front cover half moves so as to open and the rear cover half starts to fold at its hinge, the support plate supports the front cover half at its rear part with an upper end thereof. When the front cover half moves further so as to open in this state, the support plate turns backward while continuing to support the front cover half at its rear end, thereby restricting further downward movement of the front cover half. When the keyboard cover is closed, the support plate turns forward conversely while continuing to support the front cover half at its rear end as the front cover half moves forward. Then, when the keyboard cover is completely closed, the support plate moves away from the front cover half.
That is, with the conventional opening/closing mechanism for such keyboard cover, the moving front cover half must be supported at its rear part by the auxiliary mechanism when the keyboard cover is accommodated within the case. Further, in order to prevent the support plate of the auxiliary mechanism from hindering the movement of the rear cover half, the support plate must be provided turnable within the case. In addition, the front cover half must be supported at its rear part at all times by the support plate when the keyboard cover is opened/closed and when the keyboard cover is closed, the support plate must be arranged so as to move away from the front cover half.
Thus, with this conventional opening/closing mechanism, fine strict accuracies are required with which the support plate of the auxiliary mechanism is attached at a predetermined position and assembled with other associated parts as well as a wide space is required within the case where the auxiliary mechanism is provided and can operate satisfactorily. This would increase the whole size of the case. Since an obit along which the whole keyboard cover moves is formed by supporting the front cover half at its rear end with the support plate, the front cover half must be longer than the rear cover half, which increases the distance through which the front cover half moves forward and backward, thereby increasing the whole case.